Basic version of Pong

pong.py

# Implementation of classic arcade game Pong

import simplegui
import random

# initialize globals - pos and vel encode vertical info for paddles
WIDTH = 600
HEIGHT = 400
BALL_RADIUS = 20
PAD_WIDTH = 8
PAD_HEIGHT = 80
HALF_PAD_WIDTH = PAD_WIDTH / 2
HALF_PAD_HEIGHT = PAD_HEIGHT / 2
ball_pos = list()
ball_vel = list()
paddle1_pos = 0
paddle2_pos = 0
paddle1_vel = 0
paddle2_vel = 0
p1_score = 0
p2_score = 0

# initialize ball_pos and ball_vel for new bal in middle of table
# if direction is RIGHT, the ball's velocity is upper right, else upper left


def spawn_ball(direction):
    global ball_pos, ball_vel  # these are vectors stored as lists
    ball_pos = [WIDTH / 2, HEIGHT / 2]
    hval = random.randrange(2, 4)
    vval = random.randrange(-3, -1)
    if direction == 'RIGHT':
        ball_vel = [hval, vval]
    else:
        ball_vel = [-hval, vval]


# define event handlers
def new_game():
    global paddle1_pos, paddle2_pos, paddle1_vel, paddle2_vel, ball_vel  # these are numbers
    global p1_score, p2_score  # these are ints
    paddle1_pos = HEIGHT / 3
    paddle2_pos = HEIGHT / 3
    p1_score = 0
    p2_score = 0
    paddle1_vel = 0
    paddle2_vel = 0
    ball_vel = list()
    spawn_ball('RIGHT')


def draw(canvas):
    global score1, score2, paddle1_pos, paddle2_pos, ball_pos, ball_vel, p1_score, p2_score

    # draw mid line and gutters
    canvas.draw_line([WIDTH / 2, 0], [WIDTH / 2, HEIGHT], 1, "Black")
    canvas.draw_line([PAD_WIDTH, 0], [PAD_WIDTH, HEIGHT], 1, "Black")
    canvas.draw_line([WIDTH - PAD_WIDTH, 0],
                     [WIDTH - PAD_WIDTH, HEIGHT], 1, "Black")

    # update ball
    ball_pos[0] += ball_vel[0]
    ball_pos[1] += ball_vel[1]
    if ball_pos[1] <= BALL_RADIUS or HEIGHT - ball_pos[1] <= BALL_RADIUS:
        ball_vel[1] = -ball_vel[1]
    elif ball_pos[0] <= BALL_RADIUS + PAD_WIDTH:
        if ball_pos[1] >= paddle1_pos and ball_pos[1] <= paddle1_pos + PAD_HEIGHT:
            ball_vel[0] *= 1.1
            ball_vel[0] = -ball_vel[0]
        else:
            ball_vel[0] = -ball_vel[0]
            p2_score += 1
            spawn_ball('RIGHT')
    elif WIDTH - ball_pos[0] <= BALL_RADIUS + PAD_WIDTH:
        if ball_pos[1] >= paddle2_pos and ball_pos[1] <= paddle2_pos + PAD_HEIGHT:
            ball_vel[0] *= 1.1
            ball_vel[0] = -ball_vel[0]
        else:
            ball_vel[0] = -ball_vel[0]
            p1_score += 1
            spawn_ball('LEFT')

    # draw ball
    canvas.draw_circle(ball_pos, BALL_RADIUS, 2, 'Black', 'Red')

    # update paddle's vertical position, keep paddle on the screen
    paddle1_pos += paddle1_vel
    if paddle1_pos <= 0:
        paddle1_pos = 0
    elif paddle1_pos >= HEIGHT - PAD_HEIGHT:
        paddle1_pos = HEIGHT - PAD_HEIGHT
    paddle2_pos += paddle2_vel
    if paddle2_pos <= 0:
        paddle2_pos = 0
    elif paddle2_pos >= HEIGHT - PAD_HEIGHT:
        paddle2_pos = HEIGHT - PAD_HEIGHT

    paddle1_x = [HALF_PAD_WIDTH, paddle1_pos]
    paddle1_y = [HALF_PAD_WIDTH, paddle1_pos + PAD_HEIGHT]
    paddle2_x = [WIDTH - HALF_PAD_WIDTH, paddle2_pos]
    paddle2_y = [WIDTH - HALF_PAD_WIDTH, paddle2_pos + PAD_HEIGHT]

    # draw paddles
    canvas.draw_line(paddle1_x, paddle1_y, PAD_WIDTH, 'Blue')
    canvas.draw_line(paddle2_x, paddle2_y, PAD_WIDTH, 'Blue')

    # draw scores
    canvas.draw_text(str(p1_score), [200, 50], 25, 'Black')
    canvas.draw_text(str(p2_score), [500, 50], 25, 'Black')


def keydown(key):
    global paddle1_vel, paddle2_vel
    if key == simplegui.KEY_MAP['w']:
        paddle1_vel -= 3
    if key == simplegui.KEY_MAP['s']:
        paddle1_vel += 3
    if key == simplegui.KEY_MAP['up']:
        paddle2_vel -= 3
    if key == simplegui.KEY_MAP['down']:
        paddle2_vel += 3


def keyup(key):
    global paddle1_vel, paddle2_vel
    paddle1_vel = 0
    paddle2_vel = 0


def button():
    new_game()


# create frame
frame = simplegui.create_frame("Pong", WIDTH, HEIGHT)
frame.add_button('Restart', button)
frame.set_draw_handler(draw)
frame.set_keydown_handler(keydown)
frame.set_keyup_handler(keyup)
frame.set_canvas_background('White')

# start frame
new_game()
frame.start()